1. Field of the Invention
This invention relates to a design supporting (CAD) system implemented using a computer.
2. Description of the Related Art
Conventionally, in order to implement a design process, a designer first forms rough sketches called "rough sketch drawings" (NIKKAN KOGYO SHINBUNSHA, Actual Design p. 19 by Yotaro Hatamura) visualizing various design ideas to satisfy the specification, compares and studies the design ideas and selects the best one of the design ideas. After determining the design idea, the spatial arrangement, assembling method, strength and the like are studied based on the determined design idea so as to change the design idea into a more concrete and specific form.
In this process, a drawing indicating the arrangement of parts and elements to be studied is formed by handwriting on (Mylar) section paper to represent information to be designed and studied. Generally, this is implicitly effected, that is, information is represented in a form which can be understood only by the designer or a person in the design organization to which the designer belongs.
For example, in a design organization, it may be implicitly defined that the representation shown in FIG. 1A indicates the engagement of spur gears. Further, it may be implicitly defined that the representation shown in FIG. 1B indicates a convex lens, concave lens, optical axis, image-forming plane and the like. The drawing on which the above design information is represented is called a "scheme drawing".
If the required specification is satisfied in the scheme drawing, then "part drawings" for forming parts are formed based on the scheme drawing. At this time, a part drawing for a part of simple shape can be formed directly from the scheme drawing, but when a part drawing for a part of complicated shape or a moving part used in the mechanism is formed, it is necessary to define the specific shape of the part or specifically define that the part is solid or hollow. The drawing used at this time is called a "solid model definition drawing".
For example, the solid model definition drawing for a part with the shape shown in FIG. 2 may be represented as shown in FIGS. 3A and 3B.
In FIGS. 3A and 3B, the elemental surfaces constructing the part on the front and rear surfaces of the part are implicitly defined. In this case, Z=10 indicates that the surface on which it is written is a plane and the height of the surface in the Z direction is 10. In the solid model definition drawing, the boundaries between the respective surfaces are indicated.
Thus, information relating to the shape is also implicitly represented in the scheme drawing and solid model definition drawing. Therefore, with respect to standards such as the ISO standard, the drawing standard for the part drawing is perfectly provided, but the standards for the scheme drawing and the solid model definition drawing for defining the shape are not provided at all.
Recently, computers have been available for use in the above-described design process, and such CAD (Computer Aided Design) is widely used.
The CAD mainly includes 2-dimensional CAD and 3-dimensional CAD.
The 2-dimensional CAD uses a computer for effecting the drawing service which was effected in handwriting by the drafter and enhances the efficiency of the work by storing the part drawing in a data form into a file and using the stored part drawing in the later processing step or for another product. Thus, the 2-dimensional CAD is mainly used for formation of the part drawing. FIG. 4 shows the part drawing for a part of the shape shown in FIG. 2.
The 3-dimensional CAD uses a computer for storing an actual shape in a model form in the computer and make it possible to use the actual shape data more effectively than in the case of 2-dimensional CAD. That is, the 3-dimensional CAD is used to create a solid model as shown in FIG. 2.
Thus, in the present 3-dimensional CAD, it is necessary for the designer to directly input a wire frame model, surface model, or solid model on the computer image plane. If the above models are input, a mental model (image of shape) imagined by the designer and shown in FIG. 3 is displayed as a solid model on the CAD image plane and can be used for checking of interference between the parts, structure analysis (FEM) and NC machining.
However, since the 2-dimensional CAD basically contains no 3-dimensional information, it is impossible to create a solid model.
On the other hand, in the present 3-dimensional CAD, since the operating environment thereof is completely different from the operating environment of the scheme drawing and solid model definition drawing represented by the designer, the designer is required to become expert in the CAD operation or a full-time assistant is required.
Further, since CAD systems require a machine interface quite different from the conventional drawing technique effected by the drafter, it takes a longer time to make a solid model in comparison with formation of a solid model definition drawing in handwriting by the drafter, thereby imposing an extra load on the designer. Further, even after the solid model is completed, it takes a long time to change the solid model if design changes are necessary.
In addition, when a specified shape is created, the shape cannot be attained if a CAD command for the shape is not provided, and even if the solid model is completed, it cannot be used for various design examinations since the data structure of the model may not have been not made public and/or becuase the data structure has been changed by updating of the version of the CAD software so that shape definition information cannot be extracted.